Have you seen my sister?
(Book)

"Gaia Gill is the last person in the world anyone would expect to go missing. Beautiful, athletic, and recently accepted to a prestigious college, she has everything to look forward to- but the night of her going-away party at the Moon Mountain ski resort, she disappears. Gaia's younger sister Esme is supposed to be flying back to England with her family after the party, but she can't leave with Gaia missing- especially because nobody remembers Gaia leaving the party. Or if they do, they're not saying. Everyone at the lodge has their own secrets: the little rich girl, the ex-boyfriend, the ski instructor, the failed reality star. Esme's out of her depth searching the dark, dangerous forests and icy slopes of Moon Mountain, until she teams up with a local boy who promises to help her. The clock is ticking, and it's down to Esme to piece the clues together and work out who is telling the truth."--Amazon.